Is there any way to enable throttling by default while creatig new user? Currently scenario is for new user throttling is disabled.

Unfortunately, iRedAdmin-Pro doesn't support this.The idea solution is per-domain throttling for your request. Let's wait for some more days to see whether we will get an answer from Policyd mailing list.

Another solution is, you can try Policyd-2 on a testing machine, test whether per-domain throttling works for you.